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RADIATION MONITORING DEVICES
It is recommended that the installation crews use personal radiation monitoring devices. They are most
useful when working close to high power HF/VHF/UHF transmitting antennas, in order to ensure that
power has been switched off or reduced to a safe level.
There are no cumulative long-term radiation effects known for non-ionizing radiation such as microwaves.
The damage is caused only when the tissue temperature increases too much. Low level non-ionizing
radiation below the excessive heating level is not known to cause any long-term effects. In this respect
microwave radiation differs from X-ray, alpha, beta and gamma radiation, where no safe limit exists and it
is the total cumulative dosage that matters.
For monitoring microwave radiation the monitoring devices are not as useful as in case of HF/VHF/UHF
radiation. The radiation is very local. When the upper body is in front of a microwave antenna, the
monitoring device hanging on the belt may not see any significant levels even if the legal safe limit is locally
exceeded.
SAFETY DISTANCE FOR THE PUBLIC EXPOSURE
The antenna must not be installed in such a place where it causes too high exposure to the public. The safe
distance depends on the transmitter power, antenna size and frequency band. In case of iPasolink the safe
distance is presented in Table 12. The calculation assumes maximum two (2) IHG ODUs per antenna and
the assumed legal limit is 10 W/m
the safe side.
F (GHz)
0,3
6
7
13
2,5
18
3,0
23
3,9
Table 12. Safety distance in front of the antenna (metres). Two IHG ODU per antenna.
The radiation is concentrated in front of the antenna aperture and the zone to avoid is a cylinder with the
length indicated and diameter equal to antenna diameter. E.g. for a 7 GHz 3m antenna the safety zone is a
cylinder 3m by 21m in front of the antenna. In practice some extra margin should be given, especially when
it is easily available.
In reality the far field formula overestimates the power density near the antenna. Therefore the distances
are in most cases pessimistic, especially in case of large diameter antennas it may well be that the 10 W/m
limit is not exceeded at any distance from the antenna.
2
. The calculation is based on the "far field formula", which is always on
Antenna diameter (m)
0,6
1,2
1,8
3,6
7,2
10,8
4,2
8,4
12,6
4,9
9,9
14,8
6,1
12,2
7,8
15,5
2,4
3
14,4
18,0
16,8
21,0
27
2
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